Square top jibs and other sail innovations

America's Cup sail technology trickles down to the 18ft Skiffs and onwards. By Bob Ross.

While strict rules to ensure class survival by limiting costs have slowed the rate of innovation, the 18ft skiff sailors continue to explore opportunities to obtain that elusive speed edge in their rigs and sails.

The latest tweak is applying the square-top principle, seen for several seasons on mainsails, to the jibs. The two top teams in the Australian 18-Footers League Sydney fleet, Gotta Love it 7 and Thurlow Fisher Lawyers are both trying it.

Their skippers, Seve Jarvin and Michael Coxon, say they both see merit in the idea but remain cautious, even after the two boats carrying square top jibs on their small rigs cleared out from the fleet, most of which carried big rigs in the 11-15 knots nor’easter in the last race of the Australian championship.

Gotta Love it 7 won that race by 1min 43sec from Thurlow Fisher Lawyers, which had already sewn up the championship by establishing an unbeatable lead with a win in race four of the five-race series.

Daylight was third with Smeg (Nick Press), finishing 3min 17sec behind Thurlow Fisher Lawyers.

Jarvin, asked if he felt the square-top jib had made a difference, said: “It is a bit better down range, where it definitely feels good, but it is too early to judge.”

History

Square-top mains, which over several seasons replaced the pin-head top mains, evolved into bat-wing top mains, with the top batten angling the roach higher than the mast tip in the 2007-2008 season.

The mains became flatter, with less luff curve, set on stiffer carbon-fibre masts and the sail plans became more dynamic; depending on sail-cloth technology and design rather than mast bend to power-up and de-power.

The flatter moulded sails on stiffer masts allowed the big roach extended by the bat-wing top to twist off automatically in gusts while retaining control of the mid-leech.

Rig tuning became simpler on the stiffer masts, with little adjustments to the diagonal shrouds and just a few turns on the caps needed to flatten the rig off to power-up or de-power.

Michael Coxon of North Sails Australia worked with Auckland-based Southern Spars, a member of the North Marine Group, which made the masts for both Gotta Love it 7 and Thurlow Fisher Lawyers, to develop the stiffer rigs.

Coxon teamed with Gotta Love it 7’s mentor, Iain Murray, through last winter to look at the idea of square-top jibs for the 18s.

Murray, winner of the J.J. Giltinan 18ft skiff international championship a record-holding six times, as CEO of America’s Cup Race Management had recently been involved in analysing the jibs for the new AC45 multihulls with the conclusion that the square tops were more efficient than the pin-head tops.

“It seemed worthwhile having a look at it for the 18s,” said Coxon. “In winter, Iain and I took some of 7’s old jibs, recut them to square tops and saw some potential in it although it was not perfect.

“Iain and I did not want to bring it out too early. The club has a three new-sail restriction on each boat each year, which means you have to be very careful with new developments. You don’t want to build a sail that instead of being a step forward is a step backwards.”

Coxon says the theory for the square-head jib is the same as for the square-top main: It twists out at the head in a gust to de-power instead of relying on mast bend. “In the past you had to ease jib sheet to depower the jib. With the square-top the crew should not have to move the jib sheet as much.”

The square-top jib also presents a more efficient downwind profile and adds slightly more effective sail area inside the spinnaker.

Coxon and Murray chose to work with class-veteran and president of the League John Winning’s Yandoo and Seve Jarvin’s 7 team on the development. Norths built square-top jibs for Yandoo’s big rig and 7’s small rig, which were measured in on December 16, the deadline for 2011-12 season’s new sails.

Two days later, with the square-top jib on the small rig in a 10-15 knot nor’easter, 7 won the fifth heat of the club championship by a massive 4min 4sec from Thurlow Fisher Lawyers, which had enough points from the previous races to be overall winner.

The result quickly stirred interest in the square-top concept, with several teams modifying existing sails to try it. Some, including appliancesonline.com.au (Micah Lane) and Smeg (Nick Press), have simply slid the top of a re-cut to square-top jib down the forestay far enough to allow the square head to pass inside the forestay.

Yandoo, 7 and most recently Thurlow Fisher Lawyers, have used a short carbon fibre prod attached to the mast to divert the forestay outwards and create clearance for the square top between the mast and the stay.

Michael Coxon, while agreeing with the necessity for the prod, sees it also as adding tuning complications because it affects the stiffness of the topmast. “Basically, it’s early days,” he says. “It adds a new variable in mast bend with backward pressure in a new spot and may have negatives for the mainsail. It’s a variable that requires more development.”

Coxon sees the idea flowing on to other skiff and development dinghy classes. He has been trialling it on a 16ft skiff rig. “It is not an expensive item to add,” he says.

John Winning, who now has square-top jibs and mast prods on both Yandoo’s number one and number two rigs, after early misgivings believes the move is good. “We tried it first without the prod but I think the little bit of extra stiffness in the topmast is not hurting.”

Winning said using the prod also reduced sag in the forestay by shortening its loaded distance. As the mast bends, the forestay should even tighten.

Ullman’s round-head main

Another innovation tried in the 18ft skiff fleet in the 2011-12 season is the number one round-head mainsail developed by Bruce Hollis of Ullman Sails Sydney for the Rag & Famish Hotel team.

Skipper Jack Macartney explained: “We assessed the current developments at length with everything getting stiffer and bigger. We opted to go with a round-head mainsail as we felt it had the potential for better end-plating than the typical bat wing.

“Like all things in the skiffs the development requires time on the water to fine tune the rig and find the sweet spots. We are starting to get there. Working with Bruce is excellent, he is not about quantity but rather quality. His input this season has been great and we have a huge amount of confidence in his knowledge and ideas.”

The curved top is sewn over a 4mm fibreglass rod supported by two battens. Hollis says: “It is more consistently stable at the top than the bat-wing. The mains are so big and flat you are mainly working on reducing the amount of drag in the top. We are trying to make the top more efficient by reducing the tip vortex turbulence.”

Hollis and the Rag team were still working on getting the curved top to cup to windward for an end-plate effect. “We are not sure how far to go,” Hollis said.

A combination of round-head and bat-wing top was introduced to the fleet in the previous season by Jonathan Whitty, inspired by aeronautic input from his father Jeremy Whitty, an airline pilot and also a keen sailor.

A strongly curved top batten extends the top of the mainsail well above mast height for extra area and less tip-vortex turbulence.

Kiwi flight!

Across the Tasman, Auckland batten and spar maker Alex Vallings, who has always been an ideas man as well as a champion sailor in the 12ft and 18ft skiff classes, has been running a reefing mainsail in the small rig on his new C-Tech hull from the League’s builder Van Munster Boats.

Auckland is a windy place. Vallings, who has a light crew, became convinced he needed that reef in his number two rig after using one on his previous boat in that windiest of all 18ft skiff racing venues, San Francisco.

Vallings says that the reef is extremely simple to use. The mainsail has a strop at the head and two tack and clew positions at the bottom. Excess sail is simply folded over and attached onto the boom with the Cunningham eye tackle and webbing loop at the clew.

“As the sail is tight fore and aft it does not need anything in the middle like a normal reef,” says Vallings.

He has also been working on round-head tops instead of bat-wings on the mainsails of both his rigs. “This seems okay but still needs some work,” he says.

In January, Vallings won the Mark Foy Trophy championship in Auckland after having his new boat in the water only two days before the regatta, by two points from the respected American competitor Howie Hamlin, who has twice won the J.J.Giltinan international championship.

His company C-Tech also makes carbon fibre masts which, he says are 100 per cent high modulus and lighter than the other masts available. Rag & Famish, Yandoo, Asko, Smeg from the League’s fleet and Maersk Line (Graham Catley) as well as C-Tech from the Auckland Sailing Club have the latest number one rigs that are oval and stiffer than the previous season’s model.

C-Tech has a number two rig mandrel that is also oval. Vallings has the only one of these made so far.

All of which means innovation is alive and well in the 18s fleet.